Comparative Analysis of Microscopic Examination and PCR Targeting the Tams1 Gene for Detection of Theileria annulata Infection

Abstract

Bovine tropical theileriosis, caused by Theileria annulata, is an important tick-borne haemoprotozoan disease of cattle that may result in substantial morbidity and production losses. Accurate diagnosis is essential for timely therapeutic intervention and identification of infected animals, particularly when parasitaemia is low. The present study comparatively evaluated conventional microscopic examination and polymerase chain reaction (PCR) targeting the Tams1 (Theileria annulata merozoite surface antigen 1) gene for detection of infection in 210 clinically suspected cattle. Peripheral blood smears were stained with Giemsa and examined for characteristic intra-erythrocytic piroplasmic forms, while PCR was used for molecular detection of T. annulata. Microscopy detected infection in 138/210 (65.71%) animals, whereas PCR identified 162/210 (77.14%) positive animals, thereby detecting 24 additional cases not identified by microscopic examination. The difference in detection rates was statistically significant (χ² = 6.72; p < 0.01). PCR consequently yielded an 11.43 percentage-point higher detection rate than microscopy. The greater detection obtained by PCR is consistent with its ability to detect small amounts of parasite DNA and infections with low parasitaemia that may remain undetected by conventional smear examination. The findings are in agreement with previous studies reporting higher detection of T. annulata by PCR than by microscopy. Thus, Tams1-targeted PCR represents a valuable molecular approach for improved detection of T. annulata, whereas microscopy remains a simple, rapid and economical diagnostic method. A combined diagnostic strategy may therefore improve confirmation of infection and epidemiological surveillance of bovine tropical theileriosis.